﻿<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>js 图片转base64方式</title>
</head>
<body>
    <p id="container2"></p>
    <script src="lib/jquery/dist/jquery.min.js"></script>
    <script>
        let imgSrc = "http://localhost:5070/images/01.jpg";

        //width、height调用时传入具体像素值，控制大小 ,不传则默认图像大小
        function getBase64Image(img, width, height) {
            var canvas = document.createElement("canvas");
            canvas.width = width ? width : img.width;
            canvas.height = height ? height : img.height;
            var ctx = canvas.getContext("2d");
            ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
            var dataURL = canvas.toDataURL();
            return dataURL;
        }

        function getCanvasBase64(img) {
            var image = new Image();
            //至关重要
            image.crossOrigin = '';
            image.src = img;
            //至关重要
            var deferred = $.Deferred();
            if (img) {
                image.onload = function () {
                    deferred.resolve(getBase64Image(image));//将base64传给done上传处理
                    document.getElementById("container2").appendChild(image);
                }
                return deferred.promise();//问题要让onload完成后再return sessionStorage['imgTest']
            }
        }


        getCanvasBase64(imgSrc)
            .then(function (base64) {
                console.log("方式二》》》》》》》》》", base64);
            }, function (err) {
                console.log(err);
            });
    </script>
</body>
</html>
